Coal paint



Patented Feb. 27, 1945 2,s7o,42s

COAL PAINT Albert L. Stillman, Plainfleld, N. J., asslgnor to Fuel Research Corporation, a corporation of Delaware No Drawing. Application August 12, 1941, Serial No; 406,483

4 Claims.

This invention relates to the manufacture of an improved paint in which coal particles of a predetermined nature are incorporated as .the pigment or coloring substance.

Many paints when applied to a vertically disposed surface do not maintain the position in which they are brushed, but run or creep to form what is sometimes called curtains." This condition is especially likely to occur with those paints which include some form of carbon, such as, carbonized peat or lamp black, as the pigment or coloring substance and is believed to be in large part due to the fact that the types of carbon particles used in these prior paints are apt to be of such configuration as to enable them to'move' with relative ease through the liquid vehicle. Furthermore, these prior carbon paints when dry present a relatively smooth surface to which it is difiicult to apply a second coating of the same or a different type of paint without the latter creeping or running.

I have found that by utilizing as the pigment or coloring substance in the paint, coal of a special type which can be broken readily in all directions along lines of cleavage and which when pulverized produces angular particles of substantially cube-like form, and by grinding such coal together with a suitable vehicle until the paint contains a certain proportion of the coal particles below a predetermined size, I have been enabled to produce a paint which is free of the disadvantages mentioned and which is admirably suitable for use as a first or primer coating under various types of superimposed coatings.

It is therefore an object of the instant invention to provide a paint which will maintain the position in which it is brushed and will not run or creep.

Another object of the invention is to provide a primer paint to which a second or superimposed coating of ordinary commercial paint can be applied without any danger of the latter runnin or creeping.

A still further object of this invention is to provide a method of producing a satisfactory paint having ground coal as the coloring substance and having the advantages above indicated.

Further objects and advantages of the invention will appear from the following description.

As is apparent from the foregoing, one of the phases of the instant invention contemplates a paint composition in which the pigment or coloring substance consists of a coal in which cleavage is highly developed. Goals of a semi-bituminous type which have a high grindabiiity are best suited for the purposes of this invention. Bituminous coals may also be satisfactorily used if they have a high grindability or are capable of being treated, as by the use of heat, to increase their grindability to the degree desired. It may be said that'coals of the semi-bituminous or bituminous type which have a grindability of from about 50 to above on the Hardgrove scale can be satisfactorily used in accomplishin the purposes of the invention. Preferably also the coal should be a completely carbonized coal or one relatively free of resins and preferably a coal which has been substantially completely carbonized by nature, such as, upper or lower Kittanin although it is within the contemplation of the invention to use coal which has been completely carbonized by other methods. If the coal contains resins to any appreciable degree, such resins will give to the paint a, dirty brown appearance which may make the paint unsuitable for certain purposes. It is not intended, however, to place a paint including such a resinous coal as the pigment outside the scope of thisinvention provided the coal fulfills the other requirements for even though the paint may have a dirty brown appearance, other qualities imparted to the paint by such a coal will make the paint suitable for special priming coats and paint mixtures.

Inorder that a better understanding of the invention may be obtained, the following example in which the parts are by volume is given by way of illustration:

Example Take slack of a semi-bituminous coal of high grindability and substantially resin free as, for example, upper or lower Kittaning, and screen out the over-size. Then dry grind the coal in accordance with standard practice so that 85% of it will pass through a 200 mesh screen. The

ground coal is then mixed with a suitable paint cient length of time until alljof the coal goes through a screen of .at least 230 mesh. During this grinding process samples may be taken from the mix at spaced intervals to determine the size to which the coal particles have been ground. As

a specific test, cubic centimeters of the mix is removed from the grinder and the coal extracted with turpentine. The coal is then screened to determine whether it will all go through a 230 mesh screen or a screen of lower mesh if smaller coal particles are desired in the paint, for example, a 325 mesh screen. After the coal particles in the mixture have been ground in the colloidal mill to the desired size, there is added to the mixture a suitable thinner, such as, turpentine, and a suitable drier, such as, Japan oil. If the paint is to be brushed upon a surface, the ingredients of the mixture should be in approximately the following proportions:

A further small proportion of both drier and thinner added to the mixture will make the paint suitable for spraying.

A paint produced in accordance with the foregoing procedure will maintain the position in which it is brushed upon a surface and will not run or creep. This is apparently due to the angular or cube-like shapes of the coal particles which, it is believed, causes the setting up in the paint of a frictional resistance against movement of the particles to a suflicient degree to prevent flowing or running of the paint and to hold the portions of the paint substantially in the positions in which they have been brushed. The use of these angular or cube-like coal particles also gives to the surface of the paint a roughened I choring such superimposed coating to the underlying coating of paint. When the paint of the instant invention is dry it has been found to have an elasticity and resiliency such as will enable it to successfully resist breaking or cracking under relatively severe conditions, thereby rendering it suitable for use on surfaces which will be subjected to rough usage, such as for example, the

- surfaces of coal cars of the hopper type, in the use of which it is often necessary to employ a heavy implement to remove the coal after it has been maintained in the car for any length of time. Due to the fact that the'coal particles are thoroughly-and intimately mixed with the oil vehicle in the colloidal mill, such particles are protected against deterioration and will maintain the condition in which they have been ground practically indefinitely. Another advantage of the instant paint is that the particles of coal will remain stabilized in the paint vehicle for longer periods than the pigments of many prior paints. Applicant has found that by reducing the size of the coal particles so that the proportion of coal particles in the mixture under microns size is approximately from 50 to 65%, by weight, of the coal in the paint, he is enabled to obtain a paint in which th coal particles will remain stable in the vehicle for substantially long periods so that the necessity for mixing the paint before each usage is practically eliminated. A paint having the coal particles in such proportion can be obtained by subjecting the vehicle and the coal to a grinding and milling operation in the colloidal mill until the coal will all go through a 325 mesh screen. In this connection it is to be pointed out that the so-called colloidal mill is not necessarily one which is capable of reducing the coal particles to colloidal size, namely, between ,1. (micron) and 1 IL}!- in diameter. The term is an inaccurate one applied generally by the coal art to certain types of grinding mills and some so-called colloidal mills" are not even capable of reducing coal particles to a size of 325 mesh which is considerably above colloidal size. Therefore, when I speak of a colloidal mill," I mean one which is capable of reducing the coal particles so that they will pass 100% through a sieve of 325 mesh and of which particles at least 50%, by weight, will be less than 10 microns but greater than colloidal in size.

While I have referred to upper and lower Kittaning coal in the foregoing example, it will be understood that any satisfactory bituminous or semi-bituminous coal may be used and when I refer to a coal of the bituminous type in the appended claims, it will be understood to include semi-bituminous coals. For practical purposes, however, I prefer coal of high grindability, namely, a coal of a grindability above 85 on the Hardgrove scale. The proportion of the coal in the paint will naturally depend on its type and the degree to which it has been ground. I have found that in order to obtain good results the proportion of coal should not exceed 55% by volume of the mixture. It may,- of course, be less than that and may go as low as 25% by volume of the mixture for some purposes. It will thus be understood that the invention is not limited to the data given in the aforesaid illustrative example but is susceptible of many modifications and changes therefrom and is only limited in accordance with the appended claims.

I claim:

1. A paint comprising linseed oil and coal of the bituminous type which is capable of being broken readily in all directions along lines of cleavage to produce angularly-shaped particles, the coal forming approximately from 25 to 55% by volume of the paint mixture and being practically free of particles greater than 325 mesh, approximately 35% to 50%, by weight, of the coal particles being greater than 10 microns in size and, being in and of themselves incapable of remainmg in suspension in the linseed oil, and approximately 65% to 50%, by weight, of the coal particles being under 10 microns in size and capable of maintaining all the coal particles in stable, equally distributed condition throughout the paint mixture for substantially long periods.

2. A paint comprising linseed oil and coal which is capable of being broken readily in all directions along lines of cleavage to produce angularly shaped particles and which has been subjected to a grinding action in the presence of the linseed oil so that it contain substantially no particles greater than230 mesh, the coal forming from about 25 to 55%, by volume, of the paint mixture and at least 35% of said coal particles being of a size greater than 10 microns, being in and of themselves incapable of remaining suspended in the linseed oil and being angularly shaped so as to give to the surface of an applied coating of such paint a roughened or rippled quality.

3. A paint comprising linseed oil and a bituminous type coal of high grindability and capable of being broken readily in all directions along lines of cleavage to produce angularly shaped particles, the coal having been subjected to a grinding action in the presence of the linseed oil sothat it contains noparticles greater than 230 mesh and forming approximately from 25 to 55%, by volume, of the paint mixture, a substantial portion of said coal particles being of a size greater than microns, being in and of themselves incapable of remaining. suspended in the linseed oil and being angularly shaped so as to give to the surface of an applied coating of such paint a roughened or rippled quality and at least 50%, by weight, of such coal particles being not substantially greater than 10 microns and tending to maintain the particles greater than 10 microns equally distributed throughout the paint mixture.

4. A paint comprising a vegetable drying oil and coal of the bituminous type having a high grindability and capable of being broken into angularly shaped particles, the coal forming approximately from to 55%,--by volume, of the paint mixture and being practically free of particles greater than 230 mesh, approximately to by weight, of the coal particles being of a size greater than 10 microns in size, being in and of themselves incapable of remaining in suspension in the vehicle, and being capable of giving to the surface of an applied coating of such paint, a

roughened. or rippled quality, and approximately from to 50%, by weight, of the coal particles being not substantially greater than 10 microns in size and tending to maintain all of the coal particles in equally distributed condition throughout the paint mixture.

ALBERT L. STILLMAN. 

